1. Field of the Invention
The invention relates to a vehicular lamp in which a light source unit provided with at least a light emitting diode (LED) that is a light source and a reflector that reflects the light from the light source in a predetermined direction is attached to a heat sink and housed inside a lamp chamber. More particularly, the invention relates to a vehicular lamp in which a power supply substrate on which an LED chip is mounted is attached via an attachment at a predetermined position on a heat sink.
2. Description of Related Art
In recent years there has been much development with vehicular front lamps that use LEDs as light sources. In this type of front lamp, a light source unit formed of an LED as the light source and optical elements (a reflector and a projection lens and the like) that control the emitted light of the LED in a predetermined direction is integrally attached to a heat sink as a support member of the light source unit and is housed in a lamp chamber.
The LED is typically configured as a power supply substrate (hereinafter, referred to as an “LED module”) on which an LED chip is mounted. In order to stably maintain light emitting efficiency of the LED chip over an extended period of time, it is desirable to attach the LED module (i.e., the power supply substrate thereof) so that it is in close contact with the heat sink to ensure that heat is transferred to the heat sink (i.e., to ensure heat dissipation via the heat sink). In a vehicular front lamp (i.e., a light source unit), it is preferable that the LED module be accurately positioned at a predetermined position on the heat sink in order to create the proper light distribution.
In Japanese Patent Application Publication No. 2008-153080 (JP 2008-153080 A), an LED module is positioned at a predetermined position on a heat sink and attached in a closely contacting state, by covering the LED module from above with a frame-shaped flat plate attachment that has an opening in a center portion thereof, and screwing the attachment to the heat sink with the attachment surrounding the LED chip.
Also, in Japanese Patent Application Publication No. 2010-20917 (JP 2010-20917 A), an LED module is fixed with screws to a module mounting surface of a base provided on a heat sink. The LED module is accurately positioned by a plurality of pins that protrude so as to surround the module mounting surface.
However, with the technology described in JP 2008-153080 A, there is a gap, though be it small, between the LED module and the frame-shaped flat plate attachment that surrounds the LED module. As a result, there is a limit to the accuracy in positioning the LED module.
With the structure in which the LED module is positioned by pins that protrude out surrounding a module mounting surface (JP 2010-20917 A), accurate positioning is theoretically possible. However, because the heat sink having the module mounting surface with the protruding pins is formed by a die-cast product or a press formed product made of metal such as aluminum or magnesium, an R-portion 204a is formed on a base (i.e., a base portion) of a pin 204, as shown in the enlarged view in FIG. 10. That is, the pin 204 stands upright via the R-portion 204a from the module mounting surface 202 on the base (i.e., the base portion).
Therefore, a peripheral edge corner portion 206a of a power supply substrate 206 formed with a rectangular cross-section interferes with the R-portion 204a of the base (i.e., the base portion) of the pin 204, so that there is a possibility that accurate positioning cannot be performed.
More specifically, when the peripheral edge corner portion 206a of the power supply substrate 206 rides up on the R-portion 204a of the pin base (i.e., the base portion), the power supply substrate 206 is unable to closely contact the module mounting surface 202, so that there is a possibility that heat is not sufficiently transferred to the module mounting surface 202 side (i.e., the heat transfer efficiency may decrease).